Lignin is one of the most abundant biopolymers found in the planet earth. However, the residual lignin (20-30 wt % of the initial biomass) obtained after pretreatment is often overlooked as byproduct and in the paper and pulp industry and typically used for waste heat production. The structure of lignin suggests that it can be a valuable source of chemicals, particularly phenolics, which could significantly improve the economics of a biorefinery. Unfortunately depolymerization of lignin with selective bond cleavage is still the major challenge for converting it into value-added chemicals.
The current method on lignin pretreatment and depolymerization required sulfuric acid or alkali under much high temperature (e.g. 180° C.), which results in the main disadvantages of high-energy consumption and waste emission. Development of a simple, efficient and economic route to dissolve and depolymerize lignin is still a challenge.